Bovine Ac-globulin is to be isolated by methods developed in this laboratory. The purified protein is to be studied with the view of learning about its structure, and how it is digested by purified thrombin. If the hypothetical peptide(s) obtained with thrombin can be isolated, an attempt is to be made to start work on amino acid sequencing. The L and H chains can be subjected to similar study. Purified bovine thrombin is to be prepared for the purpose of studying the structural changes that occur in association with autolysis. Coagulant activity drops and esterase activity remains, and the role of active histidine is to be studied. In the case of chicken thrombin, prothrombin, prothrombin fragment 1, and prothrombin fragment 2, an attempt is to be made at getting the fragments in purified form and obtain enough amino acid sequence information to compare with comparable bovine and human material.